As the first background art, in recent years, a four-legged walking type pet robot has been proposed and developed by the applicant of the present application. Such a pet robot has a shape similar to a dog and a cat which are raised in a general home, and is adapted to be able to autonomously act in response to approach from the user such as “patting” or “petting,” a surrounding environment or the like.
Also, this pet robot is mounted with a learning function to change revelation probability of corresponding action on the basis of approaches such as “patting” and “petting” from the user, a growth function for stepwise changing the degree of difficulty of the action and the level of complicatedness on the basis of accumulation, elapsed time or the like of the approaches concerned, or the like to thereby provide high marketability and amusement characteristics as the “pet robot.”
In such a pet robot, there are prepared behavioral models consisting of individual probability state transition models for each growth stage (hereinafter, referred to as “growth stage”), and the behavioral model is switched to the behavioral model of the above described “growth stage” on the basis of approaches from the user, accumulation of elapsed time or the like to thereby express the “growth.” Also, in the pet robot, the transition probability at a corresponding place in the behavioral model is caused to change in response to approaches from the user is changed to thereby express the above described “learning.”
According to this method, however, the behavioral model is switched to a new behavioral model every time the pet robot “grows,” and therefore, the pet robot starts a new action for each “growth” as if the character was suddenly changed, and the result of the “learning” until then is to be canceled. This has led to a problem that the user, who has been used to and familiar with the action pattern until then, feels unnaturally.
Also, according to the method, even if there is any duplicate action pattern, it is necessary to prepare a behavioral model portion for the action pattern for each “growth stage,” and therefore, there is a problem that an operation for generating the behavioral model will become complicated by that much.
Therefore, if it is made possible to carry forward the action pattern or the learning result to the next “growth stage” during, for example, “growth,” it will be possible to get rid of such unnaturalness during “growth” as described above for expressing more organism-like “growth,” and it is considered that the entertainment characteristics could be that much improved.
Further, as the second background art, in recent years, a study for modeling the emotion of a human being on a computer and expressing the emotion has been vigorously promoted. As the robot technological attempts of such modeling, there have been known in Japan, the face robot of a laboratory of Fumio Hara in the Tokyo science college, or WAMOEBA 2 of a laboratory of Sugano in the Waseda University, the cat robot of OMURON Co., Ltd. or the like (“Model and Expression of Generation of Artificial Emotion” by Fumio Hara; Mathematical science, vol. 32, No. 7, page 52–58, 1994, “Study of Emotional Exchange between Human Being and Robot, Setting and Trial of Robot for Evaluation “WAMOEBA-2” by Ogata, Sugano; Lecture thesis of robotics and mechatronics lecture meeting of Japan mechanics learned society, vol. A, 1996, pp 449–452, and “Interactive Pet Robot having Emotion” by Tajima, Saito, Osumi, Kudo, Shibata; Preparatory copies of science lecture meeting of Japan Robot learned society, vol. 16, page 11–12, 1998).
In these studies, their subjects reside in how behaviors or expressions similar to those of a living thing can be obtained by initially employing already completed emotion and instinct models. However, in the case where the growth processes of the living thing are taken into consideration, it is impossible to estimate that the emotion and instinct thereof always work on the basis of the same models from a BABY period to an adult period. Therefore, the above mentioned modeling of human emotion has involved an unnatural problem from the viewpoint of “growth”.
Further, in the case where an application that an autonomous robot treated as a pet is equipped with emotion or instinct is considered, it is difficult for a user to understand and accept the robot which has initially perfect emotion and instinct. For example, in a robot having a plurality of desires (for instance, “affection desire” and “exercise desire”, etc.) as the instinct and a plurality of emotional behaviors (for instance, “joy”, “sadness” and “fear”, etc.) as the emotion, since the internal motions of the robot are complicated, the user hardly understand what the robot currently wants or how the robot currently feels.
Further, in the above robot, if the emotion and the instinct of the robot do not change and are always the same, the user is liable to lose interest in the robot. Thus, the robot is disadvantageously insufficient in view of commercialization and amusement characteristics.
Furthermore, as the third background art, there have conventionally been proposed and developed the so-called quadruped walking type pet robots which act in accordance with users' commands and surrounding environments. This kind of pet robot has a form quite similar to that of a quadruped animal such as a dog or a cat which is bred at home and is configured to assume a posture of prostration when the robot receives an order of “prostrate” and take an action of “hand lending” when the user stretches out his hand before a mouth of the robot.
By the way, such a pet robot has a model of emotion as well as a mechanism which determines an action by himself and a feature of the pet robot which can be called as a character is changed under no influence due to another robot.
Here, the character of an animal is formed under influences due to surrounding environments and when two pets are bred together, for example, existence of a pet influences largely on forming of a character of the other pet in actual circumstances.